/
defaults.go
112 lines (103 loc) · 2.81 KB
/
defaults.go
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package defaults
import (
"errors"
"reflect"
"strconv"
"time"
)
var (
errInvalidFieldType = errors.New("invalid field type")
errInvalidType = errors.New("not a struct pointer")
)
const defaultFieldName = "default"
// Set sets the default values on a struct pointed to by val. Val must be a
// struct pointer.
func Set(val interface{}) error {
if reflect.TypeOf(val).Kind() != reflect.Ptr {
return errInvalidType
}
v := reflect.ValueOf(val)
for v.Kind() == reflect.Ptr {
v = v.Elem()
}
t := v.Type()
if t.Kind() != reflect.Struct {
return errInvalidType
}
for i := 0; i < t.NumField(); i++ {
if def := t.Field(i).Tag.Get(defaultFieldName); def != "" {
setField(v.Field(i), def)
}
}
return nil
}
// NewWithDefaults copies src and returns a new struct with initialized values.
// This function is deprecated.
func NewWithDefaults(src interface{}) interface{} {
t := reflect.TypeOf(src)
clone := reflect.New(reflect.TypeOf(src))
for i := 0; i < t.NumField(); i++ {
if def := t.Field(i).Tag.Get(defaultFieldName); def != "" {
setField(clone.Elem().Field(i), def)
}
}
return clone.Elem().Interface()
}
func setField(field reflect.Value, defaultVal string) {
var iface interface{}
var err error
switch field.Kind() {
case reflect.Bool:
iface, err = strconv.ParseBool(defaultVal)
case reflect.Int:
iface, err = strconv.ParseInt(defaultVal, 10, 64)
iface = int(iface.(int64))
case reflect.Int8:
iface, err = strconv.ParseInt(defaultVal, 10, 8)
iface = int8(iface.(int64))
case reflect.Int16:
iface, err = strconv.ParseInt(defaultVal, 10, 16)
iface = int16(iface.(int64))
case reflect.Int32:
iface, err = strconv.ParseInt(defaultVal, 10, 32)
iface = int32(iface.(int64))
case reflect.Int64:
t, err := time.ParseDuration(defaultVal)
if err == nil {
iface, err = t, nil
} else {
iface, err = strconv.ParseInt(defaultVal, 10, 64)
}
case reflect.Uint:
iface, err = strconv.ParseUint(defaultVal, 10, 64)
iface = uint(iface.(uint64))
case reflect.Uint8:
iface, err = strconv.ParseUint(defaultVal, 10, 8)
iface = uint8(iface.(uint64))
case reflect.Uint16:
iface, err = strconv.ParseUint(defaultVal, 10, 16)
iface = uint16(iface.(uint64))
case reflect.Uint32:
iface, err = strconv.ParseUint(defaultVal, 10, 32)
iface = uint32(iface.(uint64))
case reflect.Uint64:
iface, err = strconv.ParseUint(defaultVal, 10, 64)
case reflect.Uintptr:
iface, err = strconv.ParseUint(defaultVal, 10, 64)
iface = uintptr(iface.(uint64))
case reflect.Float32:
iface, err = strconv.ParseFloat(defaultVal, 32)
iface = float32(iface.(float64))
case reflect.Float64:
iface, err = strconv.ParseFloat(defaultVal, 64)
case reflect.String:
iface = defaultVal
default:
err = errInvalidFieldType
}
if err == nil {
if field.CanSet() {
field.Set(reflect.ValueOf(iface))
}
}
}